Method and apparatus for flexible manufacturing a discrete curved product from feed stock

ABSTRACT

An apparatus for manufacturing a discrete curved product from a feed stock includes a source of heat that is adapted to impose a focused beam of light on at least one surface of a work piece to cause the surface of the work piece to expand and thereby move in the general direction of the heat source so as to impart a predetermined radius of curvature to the work piece. In addition, a method of manufacturing a discrete curved product from feed stock is also disclosed.

This application is a divisional of U.S. Ser. No. 09/900,075 filed Jul.6, 2001, now U.S. Pat. No. 6,622,540 which claims priority to and allbenefits from the co-pending provisional application having U.S. Ser.No. 60/216,082 filed Jul. 6, 2000 and entitled Method and Apparatus forFlexible Manufacturing a Discrete Curved Product from a Continuous FeedStock.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, generally, to a method and apparatus forflexible manufacturing and, more specifically, to a method and apparatusfor flexible manufacturing a discrete curved part from feed stock.

2. Description of the Related Art

There are numerous parts, components, and sub-components that must besubjected to one or more manufacturing steps to impart a predeterminedcurvature thereto. These manufacturing steps typically require the useof hard tooling which can include multiple progressive dies, coldheading operations, tube bending operations as well as the need forother, associated components manufactured, for example, via plasticinjection molding operations or the like. This tooling and relatedhardware as well as the batch type processing of such manufacturingoperations ultimately have a significant impact on the cost of themanufactured part.

Curved parts, components, and sub-components are commonly employed invarious automotive applications. As examples only, and not by way oflimitation, such curved parts, components and subcomponents may be foundin automotive seat frames, seat backs, brake lines, and other variousstructural elements which embody a bend in any way. One specific exampleincludes automotive windshield wiper assemblies. More specifically, itis known to employ a single, elongated, curved, homogeneous strip thatforms a spring “backbone” of the windshield wiper assembly. Suchwindshield wiper assemblies are sometimes referred to as “beam blade”type windshield wiper assemblies. The beam blade backbone is made fromspring steel and may taper both in width and thickness from its centertoward its free ends or tips. The backbone has a connecting formation ata central position for connection to a reciprocally driven arm. The armapplies a downward force and moves the blade assembly across thewindshield. The backbone is curved along a plane that is similar to theplane of curvature as that defined by the windshield. A wiper element issecured to the backbone. The thickness and width of the backbone and itsradius of curvature are preferably matched at every point along thelength of the backbone so that the backbone will provide a force perunit length distribution in a longitudinal direction which increasestoward both tips of the windshield wiper when the windshield wiper is inuse, pressed downward intermediate its ends onto either a flat orcomplexly curved surface. Beam blade windshield wiper assemblies havethe advantage of a lower profile as compared with tournament style wiperassemblies, consist of fewer parts and are considered to beaesthetically pleasing.

While such beam blade type windshield wiper assemblies have manydesirable features and advantages, they can be difficult to manufactureand, due to the hard tooling required to shape, cut and curve thebackbone, relatively expensive when compared with other conventionalwindshield wiper assemblies known in the related art.

However, the present invention overcomes these difficulties in therelated art in a method and apparatus for flexible manufacturing adiscrete curved part, such as the backbone of a beam blade windshieldwiper assembly, from a feed stock. But, from the description thatfollows, those having ordinary skill in the art will appreciate that themethod and apparatus of the present invention may be used to manufactureany discrete, curved part from a feed stock and that the invention is inno way limited to the particular application referred to above ordescribed in greater detail below. Thus, the context of a beam bladetype windshield wiper assembly as described herein is merely for examplepurposes to further illustrate the present invention, and not for anylimiting purpose.

SUMMARY OF THE INVENTION

The present invention overcomes the deficiencies in the related art in amethod and apparatus for flexible manufacturing a discrete curvedproduct from a feed stock. The apparatus includes a source of heat thatis adapted to impose a focused beam of heat on at least one surface of awork piece to cause the surface of the work piece to expand and therebymove in the general direction of the heat source and impart apredetermined radius of curvature to the work piece.

A method of manufacturing a discrete curved product from a feed stock isalso disclosed and includes the steps of providing a focused beam ofheat on at least one surface of a work piece to cause the surface of thework piece to expand and thereby move in the general direction of theheat source and thereby impart a predetermined radius of curvature tothe work piece.

Operator interface in a production line employing the method andapparatus of the present invention is minimal and consists, primarily,of monitoring the status of the production line and the product qualitybeing produced, rather than control of the process. Ideally, theproduction line includes few or no hard tools, but rather, is primarilysoftware controlled to allow changes and modifications to the endproduct's “on the fly.” Thus, as will be described in greater detailbelow, a production line employing the method and apparatus of thepresent invention is “virtually tooled” and can produce any number ofdifferent parts without stopping or even slowing the manufacturingprocess. However, those having ordinary skill in the art will appreciatefrom the description that follows that, while the reduction in the useof hard tooling is an overall, general goal of the method and apparatusof the present invention, some hard tooling may still be employed in anygiven production line without deviating from the scope of the inventionas defined in the appended claims.

Similarly, in the preferred embodiment contemplated by the inventors,the production line employing the method and apparatus of the presentinvention includes a digital signal processing computer having a neuralnetwork including a design database with predetermined manufacturingsettings that control the overall process to produce the end product.Thus, the method and apparatus of the present invention offer numerousadvantages over the traditionally hard-tooled production lines known inthe related art. Most notably, these advantages include the ability tocontinuously flow process the working material while reducing oreliminating, as much as possible, the batching processes in theproduction of a part, component or sub-component. This advantage resultsin reduced costs, waste and labor expenses. The method and apparatus ofthe present invention also provides improvements in inventory turns andmore efficient utilization of raw materials. Furthermore, the cost tomanufacture and build a production line employing the method andapparatus of the present invention is less than the cost to tool afamily of parts employed to manufacture products, such as windshieldwiper assemblies, automotive seat frames, seat backs, brake lines, benttubular products and other various structural elements that embody abend in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a perspective view of a beam blade wiper assembly having abackbone made using the method and apparatus of the present invention;

FIG. 2 is a schematic representation of a production line formanufacturing a discrete, curved part from feed stock;

FIG. 3 is a schematic view of a wound coil of spring steel;

FIG. 4 is a schematic representation of a cold rolling mill;

FIG. 5 is a schematic representation of a width profiling station;

FIG. 6 is a schematic representation of a curvature forming and heattreat station;

FIG. 7 is a schematic representation of a cutting station;

FIG. 8 is a schematic representation of a part cleaning and paintingstation; and

FIG. 9 is a flow chart illustrating each step of a flexiblemanufacturing process of the present invention as it is applied to themanufacture of a beam blade windshield wiper assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The method and apparatus of the present invention will be described ingreater detail below in connection with one possible use formanufacturing a beam blade windshield wiper assembly. However, as notedabove, those having ordinary skill in the art will appreciate from thedescription that follows that the method and apparatus of the presentinvention may be employed in connection with a number of diverseproducts and is in no way limited to the example described herein. Tothis end, a representative example of a beam blade windshield wiperassembly is generally indicated at 10 in FIG. 1, where like numbers areused to designate like structure and method steps throughout thedrawings. The beam blade windshield wiper assembly 10 includes abackbone 12 and a wiper element 14. The beam blade windshield wiperassembly 10 is controlled and driven by a spring-loaded arm, a portionof which is illustrated in both continuous and phantom lines at 16 inFIG. 1. The beam blade windshield wiper assembly 10 is mounted adjacentthe windshield (not shown) of a vehicle and pivotally driven to impartreciprocating motion to the beam blade wiper assembly 10 across thewindshield, as commonly known in the art. The backbone 12 is connectedto the arm 16 by a coupler, generally indicated at 18, which acts toreleasably connect the wiper assembly 10 to the spring loaded wiper arm16.

The elongated backbone 12 has a longitudinal beam length extendingbetween first and second ends 20, 22. The beam length defines a medianline 24 extending along the beam length. The coupler 18 is located at anintermediate position, commonly at the longitudinal center, between thefirst and second longitudinal ends 20, 22. However, those havingordinary skill in the art will appreciate that the coupler can belocated biased toward one end, 20, or the other, 22. The backbone 12 ismade of resiliently flexible material that applies a force from thespring loaded wiper arm 16 through the coupler 18 along the backbone'slength to the first and second longitudinal ends 20, 22. The backbone 12is typically made of a single, integral piece of material.

The backbone 12 includes an upper surface 26 and an opposed mountingsurface 28 with first and second sides or edges 30, 32 extendingtherebetween. Preferably, the wiper element 14 is mechanically attached,bonded, chemically attached, or otherwise adhered to the mountingsurface 28 of the backbone 12 and extends for a substantial portion ofthe longitudinal beam length. The cross-section of the backbone 12 isgenerally rectangular making the first and second sides 30, 32 generallyperpendicular to both the upper surface 26 and mounting surface 28.However, the cross-section of the backbone 12 may include any suitablegeometric shape. The backbone 12 has a width “W” defined along a widthline drawn between the first and second sides 30, 32 and perpendicularto the median line 24. The thickness of the backbone 12 is defined by animaginary line t extending perpendicular to the width between the uppersurface 26 and mounting surface 28. In general, the width and thicknessof the backbone may be consistent or the backbone may vary in widthand/or thickness along its longitudinal length.

The backbone 12 is curved longitudinally with a predetermined free formshape or radius of curvature that, when operatively disposed, extends inthe general direction of the plane of curvature of the windshield(hereinafter “windshield curvature”). An x-y plane is defined by a crosssection taken longitudinally along the median line 24 and through thebackbone 12 and wiper element 14, with the x-axis extending tangentiallyto the median line 24 at the center of the backbone 12 and the y-axisextending through the cross-section of the backbone 12 and wiper element14. A z-axis extends perpendicular to the x-y plane in the direction ofa width line drawn at the center or connecting portion of the backbone12 to the coupler 18. The curvature of the backbone 12 in the x-y planemay be symmetrical or asymmetrical depending on the force requirementsand the contour of the windshield. The flexible, free form, pre-curvedbackbone 12 flattens out, or the curvature is reduced, such that thebackbone will conform when the wiper arm 16 applies a force thereto on awindshield. Thus, the backbone 12 must have adequate free-form curvatureto ensure a good force distribution on windshields having variouscurvatures and to effect proper wrapping about the windshield.

In connection with such beam blade windshield wiper assemblies (as wellas numerous other products) there is a need to manufacture the long,thin, curved backbone 12 in a manner capable of supplying a high volumeautomotive application in an efficient, cost effective manner.Furthermore, there may be a need to manufacture such a component thatmay have a tapered shape in either or both of its width W or thicknesst. The present invention includes a method and apparatus which may beemployed to manufacture such a component and which may form a part of aflexible production line, generally indicated at 40 in FIG. 2. Ingeneral, the flexible production line 40 may be employed to manufactureany number of discrete, curved components or parts. However, theproduction line 40 will be described in the context of manufacturing acurved, backbone of a beam blade type windshield wiper assembly 10 ofthe type illustrated in FIG. 1. Those having ordinary skill in the artwill appreciate from the description that follows that the method andapparatus of the present invention may be employed to manufacture anynumber of curved parts, components and/or sub-components and that thepresent invention is not limited to automotive applications, in general,nor windshield wiper assemblies, in particular. To this end, such aproduction line 40 may include a source of a work piece, such as a woundcoil of spring steel, generally indicated at 42 (FIGS. 2 and 3); a coldrolling mill, generally indicated at 44 (FIGS. 2 and 4); a widthprofiling station, generally indicated at 46 (FIGS. 2 and 5); acurvature forming and heat treat station, generally indicated at 48(FIGS. 2 and 6); a cutting station, generally indicated at 50 (FIGS. 2and 7) and a part cleaning and painting station, generally indicated at52 (FIG. 8). Each stage of the production line 40 will now be describedin greater detail below.

Referring specifically to FIG. 3, and for purposes of manufacturing thebackbone 12, the wound coil of steel 42 is preferably a mediumcarbon-manganese spring steel, for example SAE 6150 or other low alloysteels in the medium carbon range. The coil 42 is oscillate wound offthe master coil and is butt welded and cold cross rolled at the joiningpoints. The butt weld area is annealed. The coil 42 includes a take uploop, schematically indicated at 54. The take up loop 54 is weighted toproduce a back tension in the material or work piece, schematicallyillustrated at 56, before it enters the first operation. The coil 42 mayalso include a laser vision system 55 (FIG. 4) installed over thematerial so that the butt joined area may be identified. The location ofthe butt joined areas is sent down a serial bus so that no parts will bemade from joined material.

From the coil 42, the steel working material 56 has a light film of oilrolled or sprayed onto both sides of it (schematically indicated at 57in FIGS. 4 and 9) and is then guided into the cold rolling mill 44 (FIG.4). The rolling mill 44 is designed to condition the work piece byimparting a predetermined constant or variable thickness t thereto. Tothis end, the cold rolling mill 44 may include fixed, tapered andvertical guides and programmable side rollers (schematically representedat 59). The rolling mill 44 includes a pair of opposed, rollers 58, 60which are rotatable about axes disposed generally transverse to thedirection of travel of the working material 56 as it flows through themill 44 and between the rollers 58, 60. At least one of the rollers 58,60 is movable in a direction perpendicular to the path of the workingmaterial 56 through the mill 44 and toward or away from the otherroller. More specifically, and as illustrated in the preferredembodiment of FIG. 4, the roller 60 is movably mounted to a hydraulicactuator, schematically indicated at 62. A pair of roll sensorassemblies, 64, 66, are mounted across corners to measure the separationbetween the rollers 58, 60 at 0.2 mm linear position increments of thematerial 56. The sensors 64, 66 form a part of a control system thatwill be described in greater detail below.

In the representative example disclosed herein, it is desired that thebackbone 12 taper in both width and thickness. The width of the backbone12 will be addressed at the width profiling station 46 described ingreater detail below. A tapered thickness is imparted to the steelworking material 56 at the rolling mill 44. Thus, in the preferredembodiment, the mill 44 has high stiffness, without back up rollers,because the material width of the backbone is less than 30 mm. To theextent that the thickness of the backbone varies, the variance of thematerial 56 must be controlled to plus or minus 20 μm. The material 56is always reduced by at least 0.3 mm and can be reduced as much as 1.1mm. The cold rolling mill 44 may generally be of the type disclosed inU.S. Pat. No. 5,590,566 issued on Jan. 7, 1997 and entitled, “Apparatusfor the Manufacturing of a Thin Metallic Strip”; and/or U.S. Pat. No.5,875,672 issued on Mar. 2, 1999 and entitled, “Method and Apparatus forManufacturing Metallic Support Beams for Windscreen Wiper BladeAssemblies.” Both of these patents are assigned to the assignee of thepresent invention. The disclosures of these patents are incorporatedherein by reference.

The driven rollers 58, 60 pull the material from the take up loop 54.The actual outgoing material thickness may vary depending on the desiredoperating parameters of the end product being manufactured, in thisexample, the beam blade windshield wiper assembly. Thus, the material'sthickness is also measured at 67 using a linear thickness measuringdevice. The material's actual thickness is then compared to the rollingmill's targeted thickness. Furthermore, an incremental shaft encoder,generally indicated at 68, is employed to measure the linear positiondown the axis of the semi-formed part. The separation of the rollers 58,60 is controlled by a digital signal process controller which receivesfeedback from the various sensors 64, 66, 67 and encoder 68, as will bediscussed in greater detail below.

Because of the tight thickness and thickness gradient tolerances thatmay be required to manufacture any given product, such as the backbone12, a program logic controller (PLC) cannot process the incoming sensorinformation within a desirable and acceptable time interval. Thus, adigital signal processing (DSP) computer that is capable of processingthe material thickness in real time as it is seen by the sensors, forexample, 64, 66 which measure the amount of separation between therollers 58, 60 and sensor 67 which measures the thickness of thematerial after it has passed through the rollers 58, 60, is required tocontrol the operation of the method and apparatus of the presentinvention. To this end, the digital system processing computer(schematically indicated at 71 in FIG. 9) employed with the method andapparatus of the present invention also utilizes a neural networkmachine controlled program which is fed with various thickness andposition information so that adjustments in spacing between the rollers58, 60 can be made in real time thereby allowing the thickness andthickness gradient tolerances to be held. In this way, the profile ofthe material 56 will be accurately modified so that the cold rollingmill 44 provides a semi-formed, continuous strip of metal, generallyindicated at 70, having a predetermined thickness that may vary alongthe length of the strip 70. The digital signal processing computer 71utilizing the neural network will be described in greater detail below.

Thereafter, any residual oil left on the semi-formed part 70 from thecold-rolling process may be removed as indicated at 69. Furthermore, atensioner assembly, generally indicated at 72, is employed to ensurethat the semi-formed part 70 is kept under tension and to helpstraighten out the edge curvature of the material 70. The tensionerassembly 72 has two opposed rollers 74, 76 that are controlled usingservo drive motors. The torque generated by these rollers 74, 76 issufficient to continuously move the semi-formed material 70 therethroughand can produce enough torque to provide up to 30 percent of the pullingpower for the entire rolling process. The pulling force is sufficientenough to “pull the tail straight” on the semi-formed part 70, thusremoving the edge camber of the material. Programmable side rollers 59on the incoming side of the rolling mill 44 can also be employed to helplaterally move or resist the material movement, so as to help thetensioner assembly 72 straighten the edge camber. An ink-jet marker 73may be used to selectively mark a line on the semi-formed part 70 atpredetermined places therealong to designate the end/beginning of afully formed part as will be described in greater detail below. However,those having ordinary skill in the art will appreciate that numerousother repeatable marking techniques may be employed for this purpose.For example, and as an alternative to an ink jet mark, somepredetermined physical or geometric change in the material or materialthickness or surface of the work piece may be imparted to designate thebeginning and/or the end of a fully formed part.

The semi-formed continuous strip material 70 having a variable thicknessis then transferred to the width profiling station, generally indicatedat 46 in FIGS. 2 and 5. A vision system 77 may be employed to identifythe starting point of each individual designated part (as noted by theink jet mark or other marking technique) that enters this widthprofiling station 46. A linear encoder, generally indicated at 78,rechecks the length position on the part identified by the ink. Thewidth profiling station 46 includes a cutting station, generallyindicated at 80. More specifically, and as illustrated in the preferredembodiment, a twin-headed laser 82 is mounted over the semi-formed part70 and projects the focal position of the laser optics onto the part 70.To this end, the laser 82 is mounted at a predetermined, proper heightabove the part 70 to provide an optimum cut. The twin heads are placedapart so that the optics do not interfere with each other and so thatthey can cut the part 70 to a minimum width of 4 mm. In the preferredembodiment contemplated by the inventors, the cutting station 80 employsa 2.2 KW diode pumped Nd: YAG laser, equipped with a 50/50 laser beamsplitter. The laser is remotely mounted relative to the part 70 and thelaser power is provided to the work station 46 via two fiber-opticcables (not shown). Alternatively, the cutting station 80 mayincorporate a pair of CO₂ lasers, or any other suitable cutting source.

As indicated in FIG. 5, as the laser cuts the width of the part 70, thescrap material, generally indicated at 84 is pulled down and away fromthe part 70 so that it can be cut into small pieces for disposal. Inaddition, the material 70 is notched, as indicated at 86 in FIG. 9, forpurposes of mounting the coupler 18 to the backbone 12 as describedabove. An overhead width laser measuring system, generally indicated at88, is employed to verify the actual width and position dimensions ofthe part after it has been cut by the overhead laser 82. The measuringsystem 88 uses an overhead line laser beam 90 and an underneath camera92 to measure the projected shadow of the part width. In addition,another tensioner assembly, generally indicated at 94, is employed tokeep a light tension on the part in the width profiling station 46 ofthe production line 40. However, in the preferred embodiment illustratedin this figure, the tensioner assembly 94 includes only a single servodrive motor. The width profiled material or work piece produced from thecutting station 46 is schematically represented at 96 in FIGS. 5 and 6.

In addition to the sensors and measuring system discussed above andillustrated in the figures, for any given curved component that could bemanufactured using the method and apparatus of the present invention,there may be a need for additional, similar or even different sensingand measuring systems to provide adequate feedback and control of theoverall process. For example, those having ordinary skill in the artwill appreciate that a measuring system of the type described above, andgenerally indicated at 88 in FIG. 5 as well as additional sensors of thetype described above and identified at reference numbers 67 and 68 inFIG. 4 could be added to the flexible production line 40 after thetensioner assembly 72 and before the width profiling station 46 so thatadditional data regarding the relevant characteristics of the work pieceat this point in the process may be collected and used to control theoverall process. Thus, from the overall description of the method andapparatus of the present invention contained herein, those havingordinary skill in the art will appreciate that the number, type andpurpose of the sensors described herein is not exhaustive and thatadditional like devices could be employed throughout the productionline.

Following the cutting station 46, the newly profiled material 96 is fedto the curvature forming and heat treatment station, generally indicatedat 48 in FIGS. 2 and 6. To this end, the position of the material 96 isagain identified by the paint markings or predetermined physical,geometric change in the material thickness that indicates thepredetermined beginning and end of the backbone 12 which will ultimatelybe manufactured in this representative example. Furthermore, a shaftencoder 98 (FIG. 9) is employed to re-identify the predetermined lengthof the end product and a width re-identification laser sensor isemployed for determining the center of the final product. The stripmaterial 96 may be rotated 90° (see also 100 at FIG. 9) so that it isdisposed on one of its edges 30, 32. In essence and in this example, thematerial 96 is twisted 90°. The twisting is done in the elastic range ofthe material 96 so as to impart no additional residual stresses in thepart material. However, those having ordinary skill in the art willappreciate that rotation of the part is not critical to the invention.

Next, a curvature of predetermined radius is then permanently impartedto the material 96 between its predetermined beginning and end points(see 102 at FIG. 9). This predetermined radius of curvature is impartedto the material 96 by heating one surface 104 of the material 96 so asto expand, but not necessarily melt, the material and thereafterimmediately cooling the material (see 106, FIG. 9) in a rapid fashion.For this purpose, the apparatus of the present invention includes afirst source of heat that is adapted to impose a focused beam of heat onat least one surface of a work piece. One preferred embodiment of asource of heat as contemplated by the inventors includes a laser thatproduces a diffuse beam of light directed toward at least one surface ofthe work piece. Another preferred embodiment of the first source of heatis a water-cooled, plasma, infrared lamp that also produces a beam oflight directed toward at least one surface of the work piece. A suitablewater-cooled, plasma, infrared lamp is available fromVortek-Technologies who maintain a website at www.vortek.com. Thosehaving ordinary skill in the art will appreciate that there may be othersources of heat that could be employed in the method and apparatus ofthe present invention. All that is necessary is that the first source ofheat be capable of imparting a predetermined radius of curvature to thework piece as described in greater detail below. Accordingly, thepresent invention as hereinafter further described will be presented inthe context of a laser employed as the first source of heat.

To this end, one preferred embodiment of the method and apparatus of thepresent invention employs a laser, generally indicated at 108, that isfocused on one surface 104 of the part 96. The laser 108 employs adiffused beam of oval or “line-like” configuration having a major axisextending transverse to the longitudinal axis and movement of thematerial 96. The oval shaped beam extends transverse to the surface ofthe work piece. Said another way, the beam of heat extends across, orsubstantially across, the entire width of the part. As noted above, thepower of the laser 108 is modulated and controlled so as, ideally, notto melt the surface 104 of the part 96 but rather to expand the surface104 of the material 96 upon which the beam impinges. As the one surfaceof the work piece expands, the work piece moves in the general directionof the heat source, in this case, the laser, thereby imparting apredetermined radius of curvature to the work piece. As the one surfaceof the work piece expands, it has been observed that this process causesthe material on that one surface to “gather” so as to impart the bend tothe work piece.

In the preferred embodiment, the laser is a 6 KW direct diode laser 108having an oval-shaped beam output with a length along its major axis ofapproximately 12 mm and a length across its minor axis of approximately1 mm. However, in the preferred embodiment, the beam should be sized sothat it extends across, or substantially across, the width of thesurface that is being treated. The beam is scanned along a predeterminedportion of the surface 104 of the material of each end product in thedirection of the longitudinal axis of the material 96. In the embodimentillustrated here, the material 96 moves relative to the laser beam.However, those having ordinary skill in the art will appreciate that thebeam could be moved relative to the material. Similarly, while thebackbone of the beam blade windshield wiper assembly described in detailherein may have a predetermined radius of curvature imparted theretousing a single source of heat that is scanned over the work piece in asingle pass, those having ordinary skill in the art will appreciate thatone or more sources of heat may be employed for any given applicationand that the work piece may be scanned by the beam of heat multipletimes. Furthermore, where multiple sources of heat are employed, thoseheat sources may be engaged at the same of various positions on the workpiece and may be adapted to impose both focused and defocused beamsthereon.

In any event, immediately after it has been heated by the laser 108, thesurface 104 is cooled. This process may be achieved using passive oractive cooling techniques. In the preferred embodiment, the expandedsurface 104 of the material is actively cooled using a vortex cooler110. The vortex cooler 110 is located adjacent to the point ofimpingement of the laser on the surface 104 of the material 96. Thevortex cooler 110 is of the type manufactured by Exair Corporationlocated in Cincinnati, Ohio and having a website athttp://www.exair.com. However, those having ordinary skill in the artwill appreciate that any number of suitable cooling mechanisms commonlyknown in the art may be employed for this purpose.

While the material is being heated by the laser 108, it is fullyaustenized However, when it is cooled, the material attempts to returnto its original thickness but is cooled too rapidly for this to occur.This heating/cooling process results in material forces that impart acurvature to the material 96 along its longitudinal axis. At the sametime, the rapid cooling is sufficient to produce a thorough hardnessthat is an untempered martinsite at RC 58/60. Rapid cooling results in asurface and sub-surface strain on the area of the work piece that isbeing cooled. These strains are vectored in the general direction of theconstriction. It has been noted that, since the work piece is heatedadjacent to the area that is cooled, the heated material cannot sustaina resisting strain to oppose the strain produced in the cooled area. Inthis case, the surface of the area of the work piece that is beingcooled is pulled toward the area that is being heated thereby impartinga permanent predetermined radius of curvature to the work piece. Thecurvature forming and heat treatment station 48 may therefore include acurvature-sensing system as indicated at 112 in FIGS. 6 and 9 disposedas close to the laser 108 and vortex cooler 110 as possible.

The laser power is modulated to control the actual radius of curvatureof the part being manufactured to the specified radius. To this end, thedigital signal processing controller 71 for the overall system employs aneural network software system to control the process variables,including the material thickness, width profiling, curvature and thermalexpansion properties. In one embodiment contemplated by the inventors,the neural network employed in connection with the production line 40may have one hundred or more nodes. Each node is defined by a weightedvalue and by connections to other nodes. Various weighted values may beused to simulate the nodes of a neural network, depending on the partbeing manufactured in connection with the production line 40, the typeof material employed as well as a number of other factors. Thus, theexact network configuration and weighted values will vary depending onthe specific application (e.g. type and metallurgical makeup of thematerial employed, thickness of the material, type and power of the heatsource, type of power supply, speed of the material flowing through theproduction line 40 as well as the nature and the number of sensorsemployed in the production line 40).

The input nodes of the neural network receive digital voltage signaldata in a certain, real time, window. The nodes may be either evenly ornon-linearly spaced in the time window. In any event, the neural networkis deterministic, in that a given input will always produce the sameoutput. In the example discussed herein, the neural network provides anoutput that indicates whether the thickness of material 70 produced atthe rolling mill 44 is produced within acceptable ranges; whether thewidth of the material 96 produced at the width profiling station 46 hasbeen cut within acceptable levels; whether the curvature imparted to thematerial 124 in the curvature forming and heat treat station 48 iswithin acceptable levels; and whether the part 12 has been cut to itsproper dimensions in the cutting station 50. The digital signalprocessing controller 71 adjusts various parameters at each of thesestations 44, 46, 48 and 50 by sending the required control signals tovarious sensors 55, 64, 66, 67, 68, 73, 76, 88, 98, 112 and 128 (FIG.7), as well as possibly other sensors, which control the operations ateach of these stations.

In this regard, the real time digital signal processing controller 71performs the step of comparing parameters sensed by the sensors with theparameters stored in one or more look up tables contained within thememory of the digital signal processing controller 71. The contents andformat of the look up tables will vary depending upon a number offactors including, but not limited to, the type of part beingmanufactured, the material used to manufacture the part, its thickness,the type of laser and power for the laser, etc. The contents of anygiven look up table are determined during actual pre-productionprototyping experiments. Once an entry in the look up table is foundthat matches the parameters sensed by the various sensors and fed to thedigital signal processing controller 71, the controller compares theactual reading to the information contained in its look up tables andadjusts the necessary parameters to drive the actual readings sensed bythe sensors to the desired readings contained within the look up tables.This sophisticated control apparatus allows the rolling mill 44 as wellas the lasers 80 and 108 (and lasers 116, 118 and 126 described below)to adapt their power to make the backbone 12 to the desired dimensionsand material properties.

After the predetermined radius of curvature is imparted to the material96, it is then heat-treated. Thus, the apparatus includes a temperingstation, generally indicated at 114 in FIG. 6. More specifically, thematerial 96 is then tempered back to a RC 46/50. Those having ordinaryskill in the art will appreciate that the tempering station may includeany suitable tempering device, such as traditional induction temperingdevices as well as any other tempering devices commonly known in theart. However, with respect to the embodiments disclosed herein, thetempering device is a second source of heat disposed, preferably, innon-contacting relationship to the work piece. More specifically, thetempering device may include a laser that impinges a beam of light onthe work piece thereby tempering it. Alternatively, the tempering devicemay include an infrared lamp, and preferably a water-stabilized plasmainfrared lamp.

Notwithstanding the various tempering devices that may be employed forthis purpose, in the preferred embodiment, tempering is accomplished bythe use of two, opposed direct diode lasers 116, 118 that emit a pair ofdefocused laser beams 120, 122, respectively which impart the heattreatment. It is believed that, in the preferred embodiment, thetempering process should be done using a non-contacting method so as tonot change the freeform curvature of the material 96 that has beeninduced using the laser 108. Furthermore, because the specific partcurvature and its length may vary from end product to end product, theposition of the tempering station 114 relative to the surface of thematerial 96 must float in the vertical plane of the material's normaldeflection movement. However, the focus of the beams produced by theopposed lasers 116, 118 on the opposed surfaces of the material 96 mustbe maintained at the proper distance to temper the material 96 to thespecified hardness.

The material or work piece produced at the curvature-forming andheat-treat station 48 is schematically indicated at 124 in FIGS. 6 and7. This material 124 is now complete from a thickness, width, curvatureand heat treatment standpoint. It must now be cut to a predeterminedlength. Since the individual length and curvatures of various endproducts may vary, the position in space where the material 124 is cutmust also float in both the vertical plane (due to the part curvature)as well as to its longitudinal position (due to the length changes ofthe end products). Accordingly, in the preferred embodiment, it isbelieved that the material 124 must be cut using a non-contacting methodso as not to change the curvature in the part in the upstreamcurvature-forming and heat-treating station 48. At the same time, thematerial 124 may need to be edge-supported so as not to cause ashockwave to be sent back through the material upstream from the pointthat it is being cut. Accordingly, in the preferred embodiment, themethod and apparatus employs a cutting station 50 using a cutoff laser126. A coordinate measuring system, generally indicated at 128 in FIGS.7 and 9 is employed to determine the exact position and location of thematerial prior to cutting. In the preferred embodiment, the cutoff laser126 is controlled in the X, Y, and Z axes using the DSP controller 71and its neural network. A fixture, schematically indicated at 130, maybe used to support the material 124 on one or both of its edges 30, 32so that the part does not change its freeform curvature. To this end,and in the preferred embodiment, the cutoff laser 126 is supported upona robotic arm, generally indicated at 132 which controls the cutting ofthe material in the X, Y, and Z axes. In this way, a discrete backbone12 is formed.

The individual backbones 12 are now ready to be cleaned and painted.However, prior to any painting or coating operation, the backbones 12may be subjected to additional heat treats including annealing,quenching, and/or cooling of the backbones. More specifically, and asindicated in FIG. 9, the backbones 12 may be subjected to an endtreatment 134. This may include, for example, forming a downwardlyextending, cup shaped lip portion at either end of the backbone asindicated at 136 and 138 in FIG. 9. These lip portions eliminate sharpedges and act to receive the terminal ends of the rubber wiper elements14 in the event that they extend the entire longitudinal length of thebackbone 12. In any event, the backbones 12 are next subjected to aconventional powder-coating operation 140 (FIG. 9) at a clean and paintstation 52 (FIG. 8). However, those having ordinary skill in the artwill appreciate that the backbone 12, or another part manufactured usingthe method and apparatus of the present invention, may be subject toother post forming operations without departing from the scope of theinvention. Because the backbone 12 forms the part of a visiblewindshield wiper system, its finish requirements are that of a class Asurface. Thus, the surfaces of the backbone 12 must be smooth from allprevious operations and free of any sharp edges. Furthermore, thebackbone must be free of any visible surface irregularities, which maysometimes appear as wavy marks. The edges of the backbone produced atthe width profiling station 46 must be free of drowse and, to a somewhatlesser extent, the edge scallop marks which may be produced in the lasercutting process which produces the width profile to the backbone 12. Theheat-treated surfaces of the backbone 12 must also be free of scale andshould have minimal decarborization.

In the preferred embodiment, the backbone 12 will be clamped in the partcleaning and painting station 52 and subjected to an acid dip 143 whichcleans the part as well as phosphate 144 and powder spray 146 (FIG. 9).The sprayed backbone 12 will then be baked in a conventional manner asindicated at 148 in FIGS. 8 and 9. A coupler, of the type indicated at18 in FIG. 1, is then attached to the backbone 12 (see 150 FIG. 9). Thismay include the steps of locating the backbone 12 in a predeterminedposition 158 and attaching the coupler 18 thereto to form a beam bladewindshield wiper assembly as indicated at 152 on the flow chart of FIG.9. Thereafter, a wiping element of the type indicated at 14 in FIG. 1will be mounted to the backbone 12 as indicated at 156 in FIG. 9. Withreference primarily to FIG. 9, this may include the step of locating thebackbone 12 in a predetermined position (160), applying an adhesive suchas glue to one surface of the backbone 12 (162), positioning the rubberwiping element 14 relative to the backbone 12 and applying a sufficientpressure to adhesively attach the wiping element 14 to the downwardlycurved, arcuate surface of the backbone 12 (164). The adhesive is thenallowed to cure (166). The assembly may also be subjected to a coronatreatment or other surface energy producing process, as indicated at 154in FIG. 9. Such a treatment involves the application of a high voltageto the backbone 12 at a low current. This treatment assists the bondingof the rubber wiping element 14 to the backbone 12 via the adhesive. Theassembly is thereafter available for packaging, storage, and/orshipping, as is generally indicated at 168 in FIG. 9.

The method and apparatus of the present invention is adapted toaccommodate continuous flow of the working material 56, 70, 96 and 124from the payoff coil station 42 through the cutting station 50 whereinthe backbones 12 are ready for cleaning and painting at 52. A productionline 40 employing the method and apparatus of the present invention willideally run at 10 m/min. and, it is estimated that the coil will lastfor over 50 hours. Operator interface (schematically indicated by theacronym “HMI” for Human Machine Interface in FIG. 9) will be minimal andwill consist, primarily, of monitoring the status of the production line40 and the product quality being produced, rather than control of theprocess. The production line 40 may include a limited number of hardtools, but, ideally, is software controlled to allow changes andmodification to the end products “on the fly.” Ideally, the productionline 40 described above is “virtually tooled” which can produce anynumber of different parts without stopping or even slowing themanufacturing process. The production line 40 relies on a digital signalprocessing computer 71 employing a neural network having a designdatabase including predetermined manufacturing settings which controlthe overall process to produce the end product. Thus, the method andapparatus of the present invention offer numerous advantages over thetraditionally hard-tooled production lines known in the related art.Most notably, these advantages include the ability to continuously flowprocess the material while reducing or eliminating, as much as possible,batching processes in the production of a part, component orsub-component. This results in a reduction of costs, waste and laborexpenses. The method and apparatus of the present invention alsoprovides improvements in inventory turns and more efficient utilizationof raw materials. Furthermore, the cost to manufacture and build aproduction line 40 employing the method and apparatus of the presentinvention is less than the cost to tool a family of parts employed tomanufacture products, such as windshield wiper assemblies, known in therelated art.

As noted above, the method and apparatus of the present invention may beemployed to manufacture any number of discrete, curved components orparts. And, while the method and apparatus of the present invention hasbeen described in the context of manufacturing a curved, backbone of abeam blade-type windshield wiper assembly, those having ordinary skillin the art will appreciate that the method and apparatus of the presentinvention may be employed to manufacture any number of curved parts,components and/or subcomponents and that the present invention is notlimited to automotive applications, in general, nor windshield wiperassemblies, in particular. Furthermore, it will be appreciated that thepresent invention is in no way limited to the specific type of feedstock employed in connection with the manufacture of a beam bladewindshield wiper assembly. Accordingly, the term “feed stock” as usedherein should be given its broadest possible interpretation so as toinclude, for example, but necessarily be limited to: coil stock, platestock, sheet stock, strip stock, tube stock including seamless andseam-welded, round, square, rectangular or any other geometric shape oftube stock, bar stock, cast parts, forged parts, extrusion stock,stamped stock, and wire stock. In addition, those having ordinary skillin the art will readily appreciate that the present invention may alsobe employed in spin-forming operations, roll-forming operations.Similarly, the present invention may also be employed to repair damagedmetal parts and structures, for example, highway and railroad bridgegirders, jet engine components damaged from ingested foreign objects,earthquake damaged building structures, etc. The present invention maybe employed to remove distortion caused by thermal processing such aswelding, brazing, soldering, heat treatments and the like. Those havingordinary skill in the art will also appreciate that the method andapparatus of the present invention may be employed in the forming orrepair of dies for stamping and casting operations, the forming orrepair of molds and pre-forms for fabrication of composite structuressuch as aircraft and spacecraft body and structural members, body andstructural members of boats, ships and the like. In addition, the methodand apparatus of the present invention may be employed to pre-formcomponents in preparation of other forming operations, for example,pre-bending of tubes prior to hydro-forming operations. The presentinvention may also be employed to impart surface modifications such asgrain size reduction, and may also include additional process steps suchas addition heat treatment or hardening. Furthermore, the method andapparatus may be employed in manufacturing operations that require gasand/or powder environments to impart specific surface chemistry to thework piece.

The invention has been described in an illustrative manner. It is to beunderstood that the terminology that has been used is intended to be inthe nature of words of description rather than of limitation. Manymodifications and variations of the invention are possible in light ofthe above teachings. Therefore, those having ordinary skill in the artwill appreciate that within the scope of the appended claims, theinvention may be practiced other than as specifically described.

We claim:
 1. An apparatus for manufacturing a discrete curved productfrom a feed stock, said apparatus comprising: a source of heat that isadapted to impose a focused beam of heat on at least one surface of awork piece, said beam of heat defining a major axis and a minor axis onthe work piece, said major axis of said focused beam of heat beingdisposed substantially transverse to the relative movement of the workpiece with respect to the beam of heat to cause the surface of the workpiece to expand and thereby move in the general direction of the heatsource and impart a predetermined radius of curvature to the work piece;a cooler adapted to cool the work piece after it has been heated by saidsource of heat; and a tempering device employed to temper the work pieceafter it has been cooled.
 2. An apparatus as set forth in claim 1wherein said source of heat imposes a beam of heat having substantiallyan oval shape and wherein said beam of heat substantially traverses thesurface of the work piece.
 3. An apparatus as set forth in claim 1wherein said source of heat imposes a beam of heat definingsubstantially a line of heat extending substantially transverse to atleast one surface of the work piece.
 4. An apparatus as set forth inclaim 1 wherein said source of heat is a laser that produces a diffusebeam of light directed toward at least one surface of the work piecethereby heating the work piece and causing the surface to expand suchthat the work piece moves in the direction of said laser therebyimparting a predetermined radius of curvature to the work piece.
 5. Anapparatus as set forth in claim 1 wherein said source of heat is a watercooled, plasma, infrared lamp that produces a beam of light directedtoward at least one surface of the work piece thereby heating the workpiece and causing the surface to expand such that the work piece movesin the general direction of said infrared lamp thereby imparting apredetermined radius of curvature to the work piece.
 6. An apparatus asset forth in claim 1 wherein said cooler is disposed so as to cool thework piece adjacent to the point of impingement of the focused beam ofheat on the surface of the work piece.
 7. An apparatus as set forth inclaim 1 wherein said tempering device is a second source of heatdisposed in non-contacting relationship to the work piece.
 8. Anapparatus as set forth in claim 1 wherein said tempering device is alaser that impinges a beam of light on the work piece thereby temperingthe work piece.
 9. An apparatus as set forth in claim 8 wherein saidtempering device is a pair of opposed direct diode lasers that impart apair of defocused laser beams onto the work piece.
 10. An apparatus asset forth in claim 1 wherein said tempering device is an infrared lamp.11. An apparatus as set forth in claim 1 wherein said tempering deviceis a water stabilized plasma infrared lamp.
 12. An apparatus as setforth in claim 1 further including a plurality of sensors thatoperatively sense predetermined parameters of the work piece as thepredetermined radius of curvature is imparted thereto and a neuralnetwork coupled to said plurality of sensors, said neural networkadapted to receive data sensed by said plurality of sensors, to comparethe sensed data with stored data and to generate signals to said sourceof heat thereby operatively controlling same.
 13. An apparatus formanufacturing a discrete curved product from a feed stock, saidapparatus comprising: a source of heat that is adapted to impose afocused beam of heat on at least one surface of a work piece, said beamof heat defining a major axis and a minor axis on the work piece wherethe major axis of said focused beam of heat is disposed substantiallytransverse to the relative movement of the work piece with respect tothe beam of heat, said transverse focused beam of heat acting to causethe surface of the work piece to expand and thereby move in the generaldirection of said source of heat to thereby impart a predeterminedradius of curvature to the work piece about said major axis; and acooler adapted to cool the work piece after it has been heated by saidsource of heat.
 14. An apparatus as set forth in claim 13 wherein saidsource of heat imposes a beam of heat having substantially an oval shapesuch that the beam shape defines a major axis and a minor axis andwherein said beam of heat substantially traverses the surface of thework piece.
 15. An apparatus as set forth in claim 13 wherein saidsource of heat imposes a beam of heat defining substantially a line ofheat extending substantially transverse to at least one surface of thework piece.
 16. An apparatus as set forth in claim 13 wherein saidsource of heat is a laser that produces a diffuse beam of light directedtoward at least one surface of the work piece thereby heating the workpiece and causing the surface to expand such that the work piece movesin the direction of said laser thereby imparting a predetermined radiusof curvature to the work piece.
 17. An apparatus as set forth in claim13 wherein said source of heat is a water cooled, plasma, infrared lampthat produces a beam of light directed toward at least one surface ofthe work piece thereby heating the work piece and causing the surface toexpand such that the work piece moves in the general direction of saidinfrared lamp thereby imparting a predetermined radius of curvature tothe work piece.
 18. A method of manufacturing a discrete curved productfrom a feed stock, said method comprising the steps of: providing afocused beam of heat on at least one surface of a work piece wherein thebeam of heat defines a major axis and a minor axis on the work piece andthe major axis of the focused beam of heat is disposed substantiallytransverse to the relative movement of the work piece with respect tothe beam of heat to cause the surface of the work piece to expand andthereby move in the general direction of the heat source and impart apredetermined radius of curvature to the work piece; and cooling thework piece immediately after it has been heated by the source of heat.19. A method as set forth in claim 18 further including the steps oftempering the work piece after it has been cooled.